Maybe there it is just a streak of luck but it seems to me that doing that, while discouraged removes some of the issues I usually have associated with gentoo.

As I understand dynamic linking for a system like gentoo it could potentially contribute to keeping thing from getting broken. I have, for the first time, have a system with tons of use flags and masking and unmasking things until I find the version I like doesn't break anything. Plus emerge rarely fails even when using layman.

Now anybody has an explanation why this works so well or is it just placebo?

Your binaries and libs will grow in size. And the library files will not be used very often besides compilation time.

Executables will always have the required library code available (in themselves), so they should never fail to run in that respect. And they will only have the required code, not the whole library included, provided the library is suitably structured.

Executables will not have to load dynamic libraries, which could possibly boost start-up time.

So, to me it seems that if space and sporadically used library files are not a problem, it could improve performance and reliability in many cases.
It may also seem very convenient to have programs compiled with different libraries without worrying about the presence of the libraries on the system.
However, this may have a limit depending on the final size of the executable and the respective load time, so it's hard to make a general assumption.

As usual, it's a matter of preference, space vs. convenience and some performance and load time trade-offs.

One possible issue could arise when two programs use incompatible versions of a library for communicating with each other, e.g.some dbus lib. So it's not absolutely safe.